The invention concerns the tailstock end chucking of a shaft shaped workpiece on a gear grinding machine. On account of the high accuracy that must be attained in grinding the precut and hardened gear teeth, the ends of the shafts of the gears to be ground are usually provided with centre bores which define the axis of rotation of the workpiece, and serve the accurate centralizing set-up of the workpiece. The centring via live or dead tailstock centre in the barrel or on the tailstock slide, which is pressed into the centre bore of the workpiece under a preset axial thrust, governs the radial position of the tailstock end workpiece shaft, and is of sufficient rigidity to absorb the radial machining forces when grinding the gear teeth. By way of the central application of the axial tailstock force, all bending forces on the shaft shaped workpiece and the ensuing elastic deformation of the workpiece are avoided. With this kind of work set-up, a reliable clamping and centring of the workpiece with optimum running concentricity is achieved.
In practice, however, cases can also occur in which, for example, for the sake of a less expensive manufacturing process, or on account of the pre-machining of the workpiece by centreless grinding, the centre bores at the shaft ends of the workpiece are dispensed with, and the workpiece must be centred by means of the cylindrically ground tailstock and headstock ends of the workpiece shaft. A feasible solution to this task is, for examples a centrally clamping, rotating collet on the tailstock barrel, which is actuated electromechanically, hydraulically or pneumatically after the axial advance of the tailstock to the clamping position. This solution certainly assures an exact centring of the tailstock end of the workpiece shaft, but it has the disadvantage that for the closing of the collet at the tailstock end, in addition to the axial advance of the tailstock, a power operated clamping mechanism with energy supply to a rotating component must be provided, which raises costs and reduces the reliability, occupies space in the working area of the machine, and increases the risk of soiling of the working area due to the precipitation of grinding swarf and grinding wheel dust.
The object of the present invention is to introduce a tailstock end work fixture for shafts without centre bore, using a collet of high centring accuracy, with which these disadvantages are avoided. The task is fulfilled by way of the features in accordance with the claims.